1. Field of the Invention
The present invention relates to a pattern transcription device, and more particularly, to a transcription device and a method of fabricating a cliche for the pattern transcription device being capable of forming a fine pattern without damages on the pattern.
2. Discussion of the Related Art
A flat panel display device, such as a liquid crystal display (LCD) device, includes a thin film transistor (TFT) as a switching element in each pixel. A fabricating process of the TFT requires many mask processes including a process of forming a photoresist pattern (PR). The PR pattern has a great effect on characteristics of the TFT. Characteristics of the TFT are the subject of significant research and development. Particularly, significant efforts have been devoted to improve characteristics of the TFT using a fine metal pattern.
Generally, a fabricating process of the PR pattern includes a step of forming a PR layer by coating a photosensitive PR material, a step of exposing the PR layer using a mask and a step of developing the exposed PR layer to form the PR pattern. However, since many process steps for fabricating the PR pattern, which are very complicated, are required to fabricate the TFT, production costs increase and production yield decreases.
To resolve these problems, a method of fabricating a resist pattern using a printing method is suggested. FIGs. 1A to 1D show a process of fabricating a resist pattern by a conventional reverse offset method. First, as shown in FIG. 1A, a resist material layer 32 is coated on an outer surface of a blanket 30. The blanket 30 covers along a circumference of a roller 31. The blanket 30 has a circumference being substantially the same as a length of a substrate, on which a resist pattern is to be formed.
Next, as shown in FIG. 1B, the blanket 30, on which the resist material layer 32 is coated, is rotated on a cliché 20 on a printing table 40. The cliché 20 includes a plurality of concave portions 22 and a plurality of convex portions 24 to resulting in an uneven surface. Each convex portion 24 is disposed between two adjacent concave portions 22. When the roller 31 is rotated on the cliché 20, a concave-counter pattern 34 is formed on the blanket 30 and a convex-counter pattern 36 is formed on the convex portion 24 because the resist material has a greater adhesive strength to the cliché 20 than the blanket 30. Namely, portions of the resist material layer 32 corresponding to the convex portion 24 are transferred on the convex portion 24, and the other portions of the resist material layer 32 corresponding to the concave portion 22 remain on the blanket 30, thereby forming the concave-counter pattern 34 on the blanket 30.
Next, as shown in FIG. 1C, the blanket 30 including the concave-counter pattern 34 contacts and is rotated on a process-object layer 11 disposed on a substrate 10. Then, the concave-counter pattern 34 is transferred on the process-object layer 11. By applying UV light to the concave-counter pattern 34 and hardening it, a resist pattern 38 is formed on the process-object layer 11, as shown in FIG. 1D.
Generally, the blanket 30 is formed of an elastic material, such as silicon or rubber. Accordingly, when the blanket 30 is rolled on the cliché 20, the blanket 30 is crushed and contacts a bottom surface of the concave portion 22 of the cliché 20 because of it's an elastic property, as shown in FIG. 2A, such that the resist material is partially stuck to the bottom surface of the concave portion 22 and the desired remained pattern 38 (of FIG. 1D) can not be obtained. In addition, when the blanket 30 is rolled on the cliché 20 and contacts a board between the concave portion 22 and the convex portion, the resist material layer 32 flows into the concave portion 22, as shown in FIG. 2B. Consequently, there are some undesired resist patterns on the process-object layer 11, as shown in FIG. 2C. These problems are easily caused as the resist pattern 38 is large in size.
To resolve these problems, it is possible to form the concave portions more deep so as not to contact the blanket with the bottom surface of the concave portions. However, when the concave portion has a greater depth, there are losses on a critical dimension. The concave portion is formed by a wet-etching, which has isotropic properties, using an etchant. The greater depth the concave portion has, the greater width the concave portion has. Namely, the width is proportional to the depth. It is difficult to form a fine pattern with a great width.